Method of and means for switching current-flow at high potential.



N.IJ. CONRAD.

METHOD OF AND MEANS FOR SWITCHING CURRENT FLOW AT HIGH POTENTIAL.

APPLICATION FILED FEB. 26 I91].

1,294,621. Patented Feb. 18,1919.

5 SHEETSSHEEI I.

N. J. CONRAD. METHOD OF AND MEANS FOR SWITCHING CURRENT-FLOW AT HIGHPOTENTIAL.

APPLICATION FILED FEB. 26. I9! 1. 1,294,621.

Patented Feb. 18, 1919.

5 SHEETS-SHEH 2.

.N. J. CONRAD. METHOD OF AND MEANS FOR SWITCHING CURRENT FLOW AT HIGHPOTENTIAL.-

APPLICATION FILED FEB. 26, 191i.

Patented Feb. 18, 1919.

5 SHEETSSHEEI 3 flzmfin is.

N. J. CONRAD. METHOD-0F AND MEANS FOR SWITCHING CURRENT FLOW AT HIGHPOTENTIAL.

APPLICATION FILED FEB. 25,191]- 1 ,294,621 Patented Feb. 18, 1919.

5 $HEETS-SHEEI 4.

O fl 30 K710671257" TZZdzoZaa Conrad. .1

N. J. CONRAD. METHOD. OF AND MEANS FOR SWITCHING CURRENT FLOW AT HIGHPOTENTIAL.

APPLICATION FILED FEB. 26, 191/- Patented Feb. 18, 1919.

1 ,294, 62 1 mllllljlllllllllllll i: 5HEEISSHEU 5.

UNITED STATES PATENT oriuon.

NICHOLAS J. CONRAD, OF CHICAGO, ILLINOIS, A SSIGNOR TO SCHWEI'IZER &CONRAD, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

METHOD OF AND MEANS FOR SWITCHING CURRENT-FLOW AT HIGH POTENTIAL.

Specification of Letters Patent. Patented Fb, 18, 1919.

Application filed February 26, 1917. Serial No. 151,068.

To all whom it may concern:

Be it known that I, NICHOLAS J. CONRAD, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certain new and useful Improvement in Methods of and Meansfor Switching Current-Flow at High Potential, of which the following isafull, clear, concise, and exact description, reference being had to theaccompanyin drawings, forming a part of this speci cation.

My invention relates to a novel method of and means for switchingcurrent flow at high potential.

One of the most diflicult problems in high tension electricaltransmission work is the interruption of current flow particularly inconnection with securing relief under short circuit conditions.Switching of normal current flow under high voltage is difficult enoughbut the difliculties under short circuit conditions are enormouslyincreased. The apparatus which I have chosen to illustrate my inventionis designed to operate upon voltages of the order of 100,000 to 150,000volts which at the present state of the art represent the highestcommercial transmission voltages and which present the greatestdifficulty to which switching apparatus is now subjected. The inventionit is to be understood is applicable to all voltages low or high.

The accepted manner of switching current under normal conditions is toemploy a switch having its contacts working under oil. Such switches aregenerally constructed with an overload tripping coil serially related tothe line so that in the event of excessive current flow as undershort-circuit conditions the contact of the switch may be openedautomatically. These switches as at present constructed are intended forrepeated operation but it has been found that they are subject to veryrapid deterioration and consequently are required to be inspected andrepaired at very frequent intervals. The mechanical construction isclumsy, a very considerable amount of space is required and the expenseof such switches is excessive both for initial cost and for upkeep. i

I have devised a novel method of switching high-pressure current bothfor normal switching operations and for abnormal or short-circuitconditions of operation. According to my invention oil switches as suchare dispensed with and switch units or switch links capable of only oneswitching operation are inserted in the current. That is to say Isupplant the prior permanent switch which is intended for repeatedoperation by a replaceable switch which is capable of only one operationand which must then be renewed. This is a great simplification ofexisting methods and provides much sought relief from presentdilficulties. For these individual switching units or links I employ asa basis the arc extinguishing apparatus developed by myself and EdmundO. Schweitzer as will be apparent from the patents granted to us singlyor jointly and applications now pending.

Each link or unit is a complete self-contained circuit-breaking devicecapable of one single operation having a self-supporting casing or bodybearing external terminals which are easily attached to and detachedfrom theline terminals and'containing all the mechanism required forpositively executing one successful circuitbreaking operation. Each unitafter performing its switching operation is removed for renewal whileanother unit in proper condition is inserted in the circuit.

The chief object of my invention is to provide an improved method of andmeans for switching current flow at high potential.

In carrying out the main invention above outlined I have made a numberof important improvements in apparatus and methods of operation some ofwhich are outlined in-the following objects.

It ,is a further object of my invention to provide an improved method ofinterrupting current flow at high tension. Another object is to providean improved form of automatic thermally controlled circuitbreaker. Afurther aim is to provide an improved form of circuit-breaker mount-Other objects will be apparent from the following detailedspecification.

Figure 1 represents in diagrammatic form one form of my invention whichis described in detail later;

Fig. 2 is a diagram of a modification end-- bodying my invention andshowing a shunt automatically operating upon resistance interposed bythe temperature coeflicient of a part of the shunt;

Fig. 3 is a diagram of a further modification employing theelectro-magnetic effect of the current for increasing the resistance ofthe shunt;

Fig. 1 is a diagram of the invention showing both manual and automaticmeans for increasing the resistance of the shunt;

Fig. 5 is a longitudinal section of an embodiment of my invention;

Fig. 6 is a top plan view of the same;

Fig. 7' is a fragmentary sectional view showlng the. removable ventmember;

Figs. 8, 9 and 10 are isometric views of the vent, the annular contactand the movable contact members respectively;

Fi 11 is a partly sectional and partly elevational view of the modifiedform of my invention mounted upona suitable board;

Fig. 12 is a top plan view of the switchin unit with the vent capremoved;

Fig. 13 is a detail elevational view of the removable tip;

Fig. 14 is a, sectional view of the movable contact member;

Fig. 15 is a. top plan view of the movable contact member with theliquid director connected to the same;

Fig. 16 is a top plan view of the switching unit;

Fig. 17 illustrates the manner in which the removable tip shown in F ig.13 may be manipulated;

Fig. 18 is a sectional view partly diagrammatic illustrating the mannerin which a magnetic overload circuit breaker may be mounted upon theside of the switching unit;

Fig. 19 is a front View partly in section;

Fig. 20 is a side view of a switching unit mounted upon a suitableinsulated mounting. 5

For carrying out my invention I employ as the starting point ofdevelopment of my invention the fusible circuit breaker of the typeshown in Patent No. 1008496, November 14th, 1911, granted to E. O.Schweitzer and myself.

I have found that where this type of fuse is employed for very highvoltages and to carry several hundred amperes a very large fuse must beemployed and the energy liberated by blowing of such a fuse under shortcircuit conditions is so great as to be highly undesirable within thecontainer.

I have, therefore, as a first and important conception placed the maincurrent carrying fuse outside of the container and have placed acomplete circuit 'breakinswitch within the container. This switch 1snormally held in the closed position by a wire of small diameter but ofgreat tensile strength which in itself forms a se in parallel with themain current carrying fuse. v In other words, the

main fuse forms a low resistance shunt about the auxiliary fuse. As aconsequence the current carried by the small wire which forms theauxiliary fuse is comparatively im significant and the heat generated byfusion of the same is not so great but that it can readily be sustainedin the interior of the vessel.

As a further important conception in improving that type of fuse I haveprovided means which permits manual control of the shunt about theauxiliary fuse for the purpose of causing the auxiliary fuse to blow andopen the switch; thus making the device capable of use either forautomatic overload switching or for manually controlled switchinunder'normal current.

11 order to apprise those skilled in the art how to practice myinvention I shall now describe the details of a particular embodiment inwhich my invention appears. In Fig. 1 I have shown the diagrammaticarrangement and in Figs. 5 to 10 the structural details of an automaticswitching device depending for its automatic operation upon the thermaleffect of the current.

The main body of the switchin unit shown in Fig. 5 consists of a tube ors eeve 1 of insulating material. This sleeve may be made of lassalthough on account of structural difli culties I have found that fiberimpregnated with bakelite. is preferable. A cap 2 is secured to thelower end of the sleeve and closes 03 the lower end and forms anexternal circuit terminal for the switching unit. A cap 3 surroundsthe'upper end of the sleeve land forms an external circuit terminal aswill be described later. The cap 3 is provided with a removable ventmember 4 which may be blown off by the intenor pressure within thesleeve 1 when the switch operates. The cap member 3 is pro- Vided with aprojecting bracket 5 forming at its upper end 6 a terminal for securingconductively one end of the main fuse member 7. Another bracket member 8is mounted upon the side of the sleeve 1 having its upper end 9projecting upward to substantially the level of the upper end 6. of thebracket 5 and forming a terminal for the other end of the main fuseW1thin the sleeve 1 and adjacent the upper end thereof I have mounted aconducting rlng 10 1n electrical conductive relation with the; bracket 8by means of the screws 11 which connect these parts together. The rmg 10within the sleeve 1 is provided with four sets of stationary switchcontact blades 12 which are preferably formed of flat spring metal toprovide yielding contact surface with the fins or vanes 13 of themovable terminal member 14. The movable terminal 14 is provided with adetachable stem member 15 which is connected mechanically to a coiltension spring 16, the other end of which spring is fastened to thebottom 17 of the cap member 2. A plurality of flexible conducting cables18 are connected between the stem 15 and the bottom of the cap 2 in suchmanner as to offer a path of low resistance in shunt of the spring 16.These conducting cables prevent damage to the spring 16 and at the sametime provide a path of low resistance and thereby prevent heating in thecasing 1. The movable member 14 is provided at its upper end with areduced portion 19 to which is connected a fuse 20 fastened at its upperend to the vent member 4. The fuse 20 is prefera'bl a wire of highresistance and of great tensi e strength. The function of the wire 20 isto support the movable terminal 1% in conducting relation with thestationary terminal 10 during normal condition of the switching unit.

The casing 1 is filled with an arc extinguishing liquid preferablycarbon tetrachlorid or the liquids described in the copendingapplication of Schweitzer & Conrad Serial No. 120625, filed September18, 1916, namely, poly chloro-derivatives of hydrocarbon compounds.

A flared or conical liquid director 21 is mounted upon the stem of themovable switch member 14 and serves to throw the liquid outward uponthefins or vanes 13 and about the tip 19 in such manner as to cause aviolent agitation of the liquid and to cause it to extinguish the arewhich may be drawn between the stationary terminals 12 and the movableterminal 14:.

In Fig. 1 I have shown the diagram of connections. The outgoing linewire is connected to the terminal 3 and the incoming line 22 isconnected through'the disconnecting switch 23 to the lower terminal 2.The auxiliary fuse 20 which is contained within the casing 1 and whichnormally holds the main switch l0, 14: in closed position is shunted bythe main fuse 7 which is external to the casing 1.

The operation of the switching unit is as follows: When excessivecurrent flows through the lines 21, 22, and through the switching unit,the fuse member 7 will be subjected to such a degree of heat as willmelt the metal comprising the same thereby greatly increasing thereslstance of the shunt around the fuse 20. Normally this shunt amountsalmost to a total short circuit and the high resistance of the auxiliaryfuse 2O prevents any material current flows through the same. When theresistance of the shunt is increased by fusing of the member 7 thepotential drop across the wire 20 will be increased and a flow ofcurrent through this wire sufficient to fuse the same will occur. It isto be noted in this connection that there is no intention of relyingupon the fuse 7 for breaking the of current as this function isperformed by the switch 10, let which is in series with both fuses 7 and20. This switch operates as soon as the wire 20 releases the same andpromptly opens the circuit stopping the flow of current. After thecurrent flow has been stopped the disconnecting switch 23 is opened andthe switching link is removed from the line terminals and anotherswitching unit in the proper set condition is put in its place. Thedisconnecting switch 23 is then closed.

As manual control of the switching unit is desirable manual means may beprovided for increasing the resistance of the shunt path thereby causingoperation of the switch. Such manual means may consist of a switch,rheostat or any other means for increasing the resistance of the shuntpath.

In Fig. i I have shown a rheostat 25 having a movable switch member 26in the shunt circuit, this movable member being operable to increase theresistance of the shunt by including more of the resistance of therheostat and thereby causing operation of the switch 10, 14.

The automatic operation need not be dependent upon the heatingeifectcaused by actual fusion but may depend upon the rise in resistancecaused by the temperature coefficient. In Fig. 2 I have illustrated theshunt as including a wire 27 having a large positive temperaturecoefiicient, such for instance as copper or iron or certain alloysthereof. Excessive current flow through the wire 27 raises thetemperature of the same and consequently raises the resistance to such adegree that the auxiliary fuse or releasing device 20 causes the switchto open to break the current through both paths.

The fuse 20 will operate whenever the current flow is suflicien-t. Thelow resistance shunt need not have a difi'erent coeffic1ent ofresistance to 'be completely operative but a sharper definition andgreater assurance of proper operation is secured by keeping the currentflow out of the wire 20 until the moment it is to be fused.

It is also to be understood that the increase in magnetic action may berelied upon for increasing the resistance of the shunt. I have shown inFigs. 18, 19 and 20 means dependent upon the electromagnetic forceexerted by the increased flow of current, for increasing the resistanceof the shunt. In Fig. 8 I have illustrated diagrammatically the mannerin which this may be accom-. plished. The current carrying shuntincludes a mechanical switch 29 which is of the overload release typehaving an overload coil 30 serially related to the current tial dropacross the terminals of the switch controlling fuse 20. Thisincreaseddrop of potential across the switch controlling fuse 20 causesincreased flow of current and brings about the operation of the mainswitch 10, 14.

In Fig. 18 I have illustrated a structure in which instead of employinga fusible element in the shunt path about the auxiliary fuse 20, I haveshown a magnetically controlled overload switch 29 mounted upon the sideof the casing 1 having a movable switch member 37 normally closing theconnection between the upper external terminal 3 and an auxiliaryterminal 38 which is mounted upon the side wall of the container 1 andwhich is connected through the overload trip coil 30 to a terminal ring39 that is electrically connected to the stationary. member 10 of themain switch. l have provided bracket members 40 and 41 which areconnected to the terminal members 3'and 39 respectively, and which bearelectrodes 42 and 43 so spaced that when the switch 29 is opened byexcessive current, the current will tend to cross the gap at theelectrodes 42, 43 rather than are at the switch 29 thus preventin damageto the switch. Opening of the sw1tch 29 increases the resistance of theshunt path to such an extent that a large increase of current flowsthrough the switch operating member 20 and causes opening of the mainswitch 10, 14. I

In Figs. 19 and 20 I have shown a switching unit or link 45 connected,to a suitable mounting forhigh voltage installations. A base or support46, has mounted thereupon a pair of suitable insulators 47 and 48 forthe upper and lower ends respectively of the switching unit. The upperinsulator 47 supports, by means of a clamp member 49, a board or plate50 of insulating material carrying two sets of terminals 51 and 52 thatare connected to suitable external terminals 53 and 54 of the switchingunit 45. The terminals 51 and 52 are in the form of spring clips whichengagesuitably flattened parts on the sides of the terminals 53 and 54on the switching unit 45. The upper terminal 51 is connected to the lineat 55. The insulating board 50 supports a casing 56 which. contains acircuit breaker.

57. This circuit breaker is of a type well known having carbon breakcontact 58 and laminated s ring contacts 59 and 60 and a trlpping coi 61with an adjustable trip 62.

The tripping coil is connected between the stationary contacts 59 and 60and upon the occurrence of excessive current trips out the release 62and opens the switch. I have provided a manual trip not'shown foroperating the release 62 to control manually the opening of the circuit.

The casing 56 within which the circuit breaker 57 is mounted is filledwith carbon tetrachlorid or with a liquid of the type dis= closed in theabove mentioned application of Schweitzer & Conrad. The use of thisliquid has a two-fold function. First it improves the electricaloperation in preventlng overheating and fusion of the contact parts andin quickly extinguishing the are but this is not the main reason for itsemploy:- ment. I have found that submerging the circuit breaker in abath ofthose liquids improves the mechanical operation of the same bypreventing the condensation of moisture upon the parts, by preventinggumming of the movable parts as would occur by employment of lubricatingoil, particularly at low temperatures, by keeping out dirt, insects andthe like, and by preventing the parts from oxidizing and keeping thesame in good mechanical condition.

The stationary terminals 59 and 66 of the switch 57 are connected bysuitable conduccase protect the switch 57. The lower terminal 67 of theswitching unit 45 is connected by means of a spring switch or terminal68 to the line terminal 69 mounted on the outer end of the insulator 48.

The details of the switching unit 45 are shown in Figs. 11 to 17,inclusive. A suitable insulating sleeve 1 carries at its upper end thecap member 53 which forms an external terminal that is connected to thespring clip or contact 51. Below the cap 53 a ring 54 is mounted on thesleeve 1, this ring being connected to the spring clips or terminals 52.The rin 54 is connected to an interior ring 70 which has a smoothcentral bore adapted to receive the sprin plug 71 that forms the movabletermina of the main'circuitbreaking switch 72. The movable terminal 71comprises a hollow cylindrical member slotted as shown at 73;

to provide a yielding contact within the annular terminal 70. Aremovable pin 74 is attached as by means'of screw threads to the plugmember 71 lying in the bore 75 of the member 71. This bore issubstantially larger than the size of the pin 74 so as to permit freemovement of the slotted arms portion 79 to which is connected the highresistance high tensile strength Wire 80 which supports the movableterminal 71 against the tension of the spring 16. The

pin 74 is also provided with a flattened portion 80 which permits it tobe engaged by a suitable tool 81, shown in Fig. 17, for the purpose ofsubstituting a new pin with a wire 80 properly attached, when theswitching unit is to be renewed.

The cap member 53 has an opening 82 in the top thereof, this openingbeing normally closed by a vent plug 83 which has soldered at its upperend a removable vent member 84 that is adapted to be blown ofi when thepressure in the switchin unit becomes excessive. A bridge mem er 85 onthe cap member 53 below the opening 82 is adapted to support the upperend of the wire 80 as by means of the screw 86. The vent plug 83 isprovided with suitable engaging surfaces for applying a wrench or thelike.

The spring 16 is shunted by means of suitable flexible conductors 87which are of suitable current carrying capacity.

The springv terminals 51 and 52 are mounted upon a suitable board 88which is similar to the board and is mounted in a slmilar manner and thespring terminals are connected by means of the conductors 89 and 90 tothe terminals 91 and 92 of a fusible member 93'. The terminal 91 of thefusible member 93 is connected to' a line terminal 95. The fusiblemember is mounted' directly in line with the opening in the vent member83 so that any liquid which may be ejected from the switching unit 45will tend to strike the. fusible member 93 and prevent arcing at thesame.

It can now be seen that I have provided a novel method of and means foraccomplishing the switching of current in a'high voltage system. I donot intend to be limited solely to the use of my invention in connectionwith high voltages but have described the same in connection with thehighest known voltages as illustrating the capacity of devicesconstructed in accordance with my invention to cope with the mostdifficult situation.

Heretofore in the art fuses of the type shown in rior Patent #1008496above referred to ave been provided for breaking overload current orshortcircuit current in circuits of various voltages but attention iscalled to the fact that the fusible member in that case is' designed'tocarry full load current and that the circuit is broken at the fusiblemember. In accordance with my present invention the circuit is notbroken at the fuses, or at least need not be so broken because of theprovision of the main switch which is in series with both paths which isdesigned to break the flow of current even under the most adversecondition. The switching unit of my invention is in reality a switch ofvery large capacity but of small size adapted to be inserted into thecircuit and to be opened by excessive current flow under overload orshort circuit conditions, or to be opened by a manual act when it isdesired to break the fiow of current for any other reason.

As the circuit breaking switch is completely inclosed and connected onlyelectrically with the outside parts, visual observation of the switch isnot possible. However, the condition of the shunt path reveals thecondition of the switch. If the main current carrying fuse as 7 in Fig.5 or 93 in Fig. 11 is blown then the main switch is open. Similarly ifthe switch 29 in Fig. 18 or 57 in Fig. 19 is open it will be known thatthe main switch is open.

described as there is negligible current flowf the heating negligible inthe interior 0 the casing. No damage is therefore caused by accumulationof heat.

I do not intend to be limited to the precise details shown or describedas the inrention may obviously be embodied in other forms.

What I claim is:

1. In combination a switch, a fuse normally holding the switch in closedposition, and a shunt of low resistance about said fuse.

2. In combination a switch, a fuse of relatively high resistancenormally holding the switch closed, and a shunt of low resistance aboutsaid fuse normally preventing operation of said fuse.

3. In combination a switch, means for opening said switch, a fuse ofsmall current capacity mechanically controlling said means, and a shuntof low resistance about said fuse. I

4:. In combination a switch, means for opening said switch, a fuse ofsmall current carrying capacity controlling said means, and a shunt oflow resistance electrically connected about said fuse, said shunt havingmeans for changin the relative resistance of said shunt an said 5. Incombination a switch, means for opening said switch, a fuse of smallcurrent carrying capacity controlling said mean-s, a shunt of lowresistance electrically connected about said fuse and a'fuse of largecurrent carrying capacity in said shunt.

6. In combination, a switch, means for opening said switch, a fuse ofsmall current carrying capacity controlling said means, and a shunt oflow resistance electrically connected about said fuse, said shunt havingautomatic means for increasingv the resistance of the shunt.

7. In combination, a switch, means for opening said switch, a fuse ofsmall current carrying capacity controlling said means and a shunt oflow resistance electrically connected about said fuse, said shuntcomprising means for increasing the resistance of the shunt and therebyincreasing the current flow through the fuse.

8. In combination, a switch, means for opening said switch, currentoperated means of relatively high resistance controlling said switchopening means, an inlclosing casing for said switch, said opening meansand said controlling means, and a shunt of low resistance and relativelylarge current capacity external to said casing connected about saidfuse.

9. In combination, a switch, means for opening said switch, currentoperated means of relatively high resistance controlling said switchopening means, an. inclosing.

casing for said switch, said opening means and said controlling means, abody of arc extinguishing liquid in said casing and a shunt of lowresistance and relatively great current carrying capacity external tosaid casing and connected about said fuse, said shunt comprising afusible member.

10. In combination, a switch, a spring for operating the switch, a fuseof high tensile strength holdingsaid switch closed, a casing inclosingthe switch, the spring and the fuse, and an external shunt about saidfuse.

11. In combination, a switch comprising stationary and movableterminals, a spring connected to the movable terminal, a fuse of hightensile strength holding said movable terminals in engagement with thestationary terminals, a casing inclosing the switch, the spring and'thefuse, said stationary terminals being mounted on the -inside of saidTeasing and an external shunt about said fuse.

12. In combination a switch, a spring for opening the switch, a fuse ofhigh tensile strength holding said switch in closed position, a casinginclosing said switch and.

said spring, a shunt exterior to the casing, said shunt being connectedabout said fuse, and an arc extinguishing liquid in said casing.

13. In combination a switch having a movable element a spring foroperating the mova-ble element of said switch, a fuse of high tensilestrength holding said switch in closed position, a casing inclosing theswitch and the spring, a body of liquid in the casing and means forprojecting said liquid upon the are drawn by the movable element of saidswitch.

14. In combination, a casing comprising a tubular sleeve of insulatingmaterial, a terminal member encircling the upper end of said sleeve, aterminal member encircling the lower end of the sleeve closing off thesame to form a liquid tight container, a switch in said container, saidswitch comprising a stationary member secured to the wall of said casingand a movable member normally in contact with said stationary member,means in said casing for separating said switch members, a fuse in saidcasing holding said switch members normally in contact, and an externalfuse of low resistance shunting first said fuse.

15. In combination, a tubular member of insulation, a metallic capclosing off the lower end of said tubular member, a metallic cap closingoff the upper end of said tubular member, a stationary switch contact insaid tubular member secured to the walls thereof, a movable switchmember adapted to engage said stationary switch member, a

fuse member of small capacity connected between the upper cap and saidmovable contact member, means for separating said switch contact, aterminal member mounted upon the outside of the tubular member and ashunt of low resistance connecting said terminal member and said uppercap member.

16. In combination, a tubular sleeve of insulation, a terminal capclosing off the bottom of said sleeve, a terminal cap closing off thetop of said sleeve, said upper terminal cap having an axial opening andhaving a vent plug for closing said opening, a supporting memberconnected to the terminal cap below said axial opening, a switch in saidtubular sleeve, said switch comprising a relatively stationary memberand a. relatively movable member and a wire of small diameter and ofrelatively high tensile strength connected between the movable switchmember and the supporting member.

17. In combination, a tubular sleeve of .insulation, a switch mounted insaid sleeve adjacent the upper end thereof, said switch comprising arelatively stationary and a relatively movable member, a terminal capclosing off the top of the sleeve, said cap having a supporting member,and a Wire of relatively high resistance and high tensile strengthconnecting the movable switch member with said supporting member.

18. In combination, a tubular sleeve of insulation, a metallic capclosing one end of the sleeve and forming an external terminal,

a stationary switch member comprising an annular contact'mountedadjacent the one end of the sleeve, a movable switch member comprising ayielding plug for engaging said annular contact, and a fuse member ofsmall current carrying capacity connecting the movable switch memberwith the metallic cap and holding said switch'in closed position.

19. In combination, a tubular sleeve of insulation, an annularstationary switch member mounted near one end of said sleeve, arelatively movable plug member adapted to engage said stationary annularmember, a spring for moving said movable member, a liquid directorsurrounding said movable member, a metallic external terminal at saidone end of the sleeve and a fuse of small current carrying capacityconnected between the movable switch member and saidterminal.

20. In a device of the class described, a sleeve of insulation, a capmember adapted to close the end of said sleeve, said cap hav- -ing anaxial hole, a' supporting member across said axial hole, a stationaryswitch member mounted on the interior of the sleeve independently of thecap, a vent plug removablysecured in said axial hole, said vent plughaving a relatively large passage adapted to be opened by excessivepressure and having a disk covering said opening and a movable switchelement contained in said sleeve. 7

21. In combination, a tubular sleeve of insulation, a metallic capmember closing off the top of the sleeve, a switch in said sleeve, saidswitch comprising a stationary member mounted on the side walls of thesleeve, and a movable member adapted to contact with said stationarymember said movable member having a separable tip and a fusible memberconnecting said tip to said metallic cap member. 1

22. In combination, a sleeve of insulation, a metallic cap for saidsleeve, a switch in said sleeve, said switch comprising'an annularstationary contact, and a movable contact, said movable contactcomprising a plurality of yielding spring fingers, and a removable pinmounted centrally of said fingers, and a fusible member connecting saidpin to the metallic cap.

23. In combination, a sleeve of insulation, a metallic cap for saidsleeve, an annular stationary switch contact mounted in said sleeveadjacent the end thereof, a movable contact member for engaging saidstationary contact, said movable member comprising a cylinder ofconducting material having a hollow bore for a part of its length andhaving slots cut substantially radially to provide a plurality of springfingers, and a removable tip mounted independently of said springfingers on the contact member.

ing slots cu-t substantially radially to provide a plurality of springfingers, and a removable tip mounted independently of said springfingers on the contact member, said movable member having passagewaysfor an arc extinguishing liquid through the side walls thereof and aliquid director secured to said movable member.

25. In combination, a: switch having a movable element, a currentcontrolled member of relatively low resistance in series with saidswitch,a shunt of high resistance about said member and connected to themovable element of the switch.

26. In combination, a switch having a pair of contacts, including amovable contact, a control element for said switch, said control elementbeing connected electrically to the movable contact of said switch andnormally restraining theswitch from opening, and a shunt of lowresistance about said control element.

27. In combination, a switch comprising a movable and a stationarycontact, a marginal current operated control element for said switchhaving two terminals and having one terminal connected to said movablecontact and a shunt of low resistance connected between the otherterminal of the control element and the stationary switch contact. s p

28. In combination, a switch comprising a movable and a stationarycontact, a marginal'burrent operated control element for said switch,having one terminal connected to said movable contact, a shunt of lowresistance connected between the other ter-.

minal of the control element and the stationary switch contact, andmeans for automatically increasing the resistance of said shunt uponexcessive current flow through the switch.

29. In combination, a switch having a movable and a stationary contact,terminals for said contacts, means tending at all times to move themovable contact toward the open position, are extinguishing means forthe switch, brought into action by movement of the movable contact,fusible meansfor mechanically holding the contacts in engagement, saidmeans being connected electrically between the line and one of thecontacts and a second fusible means connected between the terminal forthe stationary contact and the line.

30. In combination, a switch comprising a movable contact and acooperating contact, a terminal, a fusi ble link governing the movementof the movable contact, said link being connected between said terminaland one of the switch contacts, and a fusible link of greater currentcarrying capacity coripected 1n shunt about said first fusible lin 31.In combination, a switch comprising a movable contact and acooperatingcontact, a terminal, a fusible link controlling the movement of themovable contact, said link being connected between said terminal and oneof said switch contacts, and a fusible link of greater current carryingcapacity connected between the terminal and the cooperating Twitchcontact in shunt of said first fusible ink.

32. In combination, a switch comprising a movable contact and acooperating contact, a terminal, a fusible link governing the movementof the movable contact, said link being connected between said terminaland one of the switch contacts, and a shunt containing a device forautomatically increasing the resistance of the shunt upon excessivecurrent fiow connected between the terminal and the cooperating switchcontact.

33. In combination, a switch comprising movable and stationary contacts,a terminal, a control element for the switch, connected between theterminal and the movable contact, and a shunt for the control elementconnected across the terminal and the stationary contact, said shuntcomprising a conductor adapted to increase the resistance of the shuntwhen the switch is to be operated. 1

3%. In combination, a switch comprising movable and stationary contacts,a terminal, a control element for the switch, connected between theterminal and the movable contact, and a shunt tor the control elementconnected across the terminal and the stationary contact, said shunthaving means for automatically increasing the resistance of the shuntupon excessive current flow to cause the release element to operate.

35. In combination, a terminal, a switch comprising a movable contactand a cooperating contact, said movable contact being biased to openposition, an element governmg the movement of said movable contact andbeing electrically connected between said movable. contact and saidterminal and a member of relatively low resistance connected betweensaid terminal and the cooperating contact of the switch,

36. In combination a. switch adapted to be connected in series in aline, said switch having a movable contact, a controlling element-mechanically restraining the movable element against movement, said;controlling element comprising a fusible conductor of rel atively highresistance, serially related to the line, and a shunt of low resistanceabout the controlling element.

37. In combination, a switch having a movable contact, a controllingelement mechanically restraining the movable contact from movement, saidcontrolling element comprising a fusible conductor of relatively highresistance serially related to the line, a shunt of low resistance aboutthe controlling element and means forming a part of the shunt forincreasing the resistance of the shunt.

38. In combination, a tubular casing. of insulation forming a cylinder,a first main terminal at one end of the casing, a second main terminalat the other end of the casing, a piston member guided in said tubularcasing, a movable switch contact carried by said piston, a stationaryswitch contact in the casing, a spring for moving said piston and saidmovable contact, said cylinder containing an arc extinguishing fluid andmeans for projecting the fluid into the space between the stationary andthe movable contacts.

39. In combination, a tubular casing of insulation, a firstmain terminalat one end of the casing, a second main terminal. at the other end ofthe casing, a piston member guided in said tubular casing, a movableswitch contact carried by said piston, a stationary contact in thecasing, a sprlng for moving said piston and said movable contact, saidcasing being adapted to contain a body of fluid for extinguishing thearc, and

means carried by the piston for projecting the fluid into the spacewhere the arc is formed.

40. In combination a tubular casing of insulation, a stationary switchcontact in said casing, a piston member in said casing, a movable switchcontact carried by said piston and adapted to cooperate with thestationary contact, a spring for moving said piston and movable contactaway from the stationary contact and fusible means normally holding saidswitch contact together.

41. In combination, a tubular casing of insulation, a switch terminalsecured at one end of the casing, a stationary switch contact in saidcasing, a piston member guided in said tubular casing, said pistonmember hearing a movable switch contact adapted to cooperate with saidstationary switch contact, spring means for moving said piston and aidmovable contact away from the stationary contact, said casing beingadaptto'centain a body of fluid for extinguishing the arc, said movableswitch contact having a hollow bore for the discharge of fluid into thepath the d2. In combination, insulation, a stationary contac ing, aplston in said 5, contact carried by niar switch enring means currentcontrolled means for holding the tubular contact normally in engagementwith the stationary contact.

43. The method of controlling a switch,

which consists in holding the switch closed with a fusible elementserially related to the switch, then shunting a part of the currentabout said fusible element, then increasing resistance of the shunt tothrow sufficient current through the fusible element to fuse the same.

, 44. In combination, a switch, means tending normally to open theswitch, and a fusible mechanically restraining element for said switch,said element being connected electrically in series with the switch.

45. In combination, a switch, means tending to open the switch, acurrent controlled mechanically restraining element for said switch,said element being connected electrically in series with the switch, anda shunt of low resistance about said element, said shunt comprisingmeans for automatically increasing the resistance of the shunt uponexcessive current flow. Y 46. In combination, a switch and a currentcontrolled governing element for governing-the opemng of the switch,said element being connected electrically in series with the switch, acasing inclosing the switch and said elements, a body of fluid in thecasing and means for automatically projecting said fluid upon the arewhen said switch is opened.

47. In combination, a switch, a current controlled governing element formechanically governing the opening of the switch, said element beinconnected electrically in series with the switch, and means connected inparallel with the element for controlling the flow of current throughsaid element, said means comprising a device for automaticallyincreasing the resistance of the shunt upon excessive current flow.

48. The method of controlling a switch which consists in holding theswitch closed with a fusible element serially related to the switch,then shunting a part of the cur-. rent about said fusible element, thenincreasing resistance of the shunt to throw suflicient current to thefusible element, then fusing said fusible element to release the switch.

49. In combination, a switch adapted to be connected in series in aline, means controlling the opening of said switch, a fuse of relativelysmall current carrying capacity governing the operation of saidcontrollin means, a shunt of low resistance about sai fuse, said shuntand said fuse being connected in parallel with each other and in serieswith the line, the portion of the parallel circuit including the fusebeing of relatively much higher resistance than that of, the shunt andsaid shunt comprising means for increasing the ratio of the resistanceof the shunt with respect to the resistance of that portion of theparallel circuit including the fuse.

In witness whereof I hereunto subscribe my name this 23rd day ofFebruary, A. D.,

NICHOLAS J. comm).

